1. Technical Field
The present disclosure is related to a dimming circuit. More particularly, the present disclosure is related to a dimming circuit for a light emitting diode.
2. Description of Related Art
In recent times, due to the advantages of the light emitting diode such as high efficiency, and ability of energy saving, light emitting diodes have replaced traditional lighting sources in many applications and have become an important area of research.
The dimming circuit of a light emitting diode nowadays uses an operational amplifier during the dimming process. Please refer to FIG. 6, which is the characteristic curve of an output voltage Vo versus an input voltage Vi of an operational amplifier. As shown in FIG. 6, when the input voltage Vi is lower than a threshold voltage VT1 or higher than a threshold voltage VT2, the output voltage Vo is equal to the saturated voltage −Vsat or the saturated voltage Vsat, respectively. In other words, the operational amplifier is in the linear working region only when the input voltage Vi is within the range between the threshold voltage VT1 and the threshold voltage VT2, and it is in the non-linear working region either when the input voltage Vi is too high or too low. When the operational amplifier operates in the non-linear working region, the dimming circuit is not capable of properly control the light emitting diode, resulting in problems such as light source flickering and control failure.
Accordingly, ways in which to improve the structure of the existing dimming circuit are important research issues and urgent objects in the relevant field.